I had my 1st baby at 15yrs old, I'm married to her father, we are ready for our 2nd baby and have been trying for some time now... is it me? How can we improve our chances of concieving?

There are higher chances of you conceiving this time just take time to seek your doctor's opinion on reproductive health status of both you and your spouse. Then you can consider having sex around your ovulation dates and if possible for the whole of that week before and after your ovulation.

How long is a long time? Where you on birth control before and how long off?
Are you properly tracking your fertile times to help improve the odds?